A family asked Massachusetts' highest court Wednesday to ban the daily practice of reciting the Pledge of Allegiance in public schools, arguing that the words ''under God'' in the pledge discriminate against atheists.

In arguments before the Supreme Judicial Court, a lawyer for an atheist Acton couple who sued on behalf of their three children argued that the reference to God suggests that ''good patriots are God believers'' and nonbelievers are less patriotic or unpatriotic.

David Niose, an attorney representing the family and the American Humanist Association, rejected the argument that because the pledge is voluntary, it does not discriminate against atheists.

A lawyer for the Acton-Boxborough Regional School District argued that the pledge is not mandatory and students can opt out by either leaving out the reference to God or by not reciting the pledge.

''There is no religious bias in the statute,'' said Geoffrey Bok, an attorney for the school district.

Wednesday's court proceeding was an appeal of a 2012 Middlesex Superior Court ruling that the rights of the couple's children were not violated by the words "under God" when the pledge was recited at their schools. The lower court also found that the pledge did not violate state law or the school's anti-discrimination policy.

The phrase "under God" was added to the pledge in 1954 by Congress after a lobbying effort by the Knights of Columbus.

The American Civil Liberties Union of Massachusetts has declined to comment on the case.

Ralph Hicks, superintendent of the Ashburnham Westminster Regional School District, said he has never thought of the Pledge of Allegiance as a prayer, even though it contains the phrase "under God."

"I'm Catholic. And when I kneel down on Sunday, I don't say the pledge. I have real prayers ... real prayers," he emphasized. "Whether you're Christian, Jewish or Muslim, it would be hard to find that that is a prayer. That's a stretch."

Massachusetts requires that the American flag be flown in public school classrooms. Teachers are asked to lead students in saying the Pledge of Allegiance each day. But students and teachers are not required to recite the pledge.

June Eressy, principal at Chandler Elementary School in Worcester, said students are told at the beginning of the school year that they're not obligated to say the pledge.

"We just rise and say, 'Join us in the pledge.' And if they choose not to say the pledge, they just stand. It really isn't an issue here at all," she said.

But when she was principal at a middle school and at a high school, there were some issues.

"Sometimes I ran into some kids that didn't want to stand. I'd say, 'That's fine. You don't have to,'" said Ms. Eressy.

According to the Worcester public schools' policies handbook: "It is the policy of the Worcester Public Schools that the Pledge of Allegiance be recited and a 'Moment of Silence' be observed at all levels on a daily basis in the Worcester Public Schools."

In practice, Superintendent Melinda J. Boone said, a student is welcome to simply stand and remain silent during the pledge. "We just ask you to observe the time," Ms. Boone said.

The district weighs any religious considerations a student might have, she said.

Stephen E. Mills, superintendent of the Acton-Boxboro school district, defendant in the lawsuit, said the plaintiff couple allege that their children are required to say "under God," when they recite the Pledge of Allegiance.

"Not only are they not required to say 'under God,' they are not even required to say the Pledge of Allegiance," he said.

Mr. Mills said he does not know who the parents are. He said they never complained to anyone within the district before filing the lawsuit. He said that during the 36 years he has been in education, including seven years as deputy superintendent in Worcester, he has never had a parent complain that a child was being mistreated for participating in the Pledge of Allegiance or for not participating, he said.

"The kids know it's voluntary. They see some of their classmates opting out," he said. "Some kids will say to a teacher, 'My parents don't want me to say that.' We say, 'That's fine.' It's a non-issue.

"Over the three years this has been going on, it has cost us $60,000 to defend the school district. I could hire a teacher with that money," added Mr. Mills.

Kevin Kearney, a member of the Grafton Street School Council in Worcester, said he sees no problem with the pledge containing the word "God."

"It's perfectly acceptable to say that in school. It says that on all the currency, 'In God we trust.'"

Eric Rassbach, deputy general counsel for The Becket Fund for Religious Liberty, told the justices that the phrase ''under God'' has a long history as an expression of a ''political philosophy'' and is not a religious declaration.

''It's always been used to limit first the power of the king and now the power of government,'' Rassbach said after the hearing. ''It's not a religious statement ... no one is getting up there and saying a prayer when they say the Pledge of Allegiance.''

Last year, a Massachusetts judge found that the words ''under God'' in the pledge did not violate state law or the school's anti-discrimination policy. Judge S. Jane Haggerty found that including ''under God'' in a voluntary patriotic exercise does not ''convert the exercise into a prayer.''

The family appealed the ruling.

The case stems from a lawsuit filed by the couple in 2010. Their name was not disclosed.

Niose said the family is seeking a ruling that declares unconstitutional the current daily classroom recitation of the pledge.

The original pledge was adopted by Congress in 1942 and did not contain the words ''under God.''

The phrase was added in 1954.

The justices peppered Niose with questions about how far the ban on the pledge should extend, noting that the pledge is recited at sporting events and other public gatherings.

Chief Justice Roderick Ireland noted that there are other references to God made in public places, including at state courthouses where court officers include ''God save the Commonwealth of Massachusetts.''

Niose said those references are ''ceremonial'' and not recited on a daily basis by children for their 13 years in public school.

The court did not immediately rule. Decisions typically are published several months after oral arguments.

Any ruling by the court would apply only to Massachusetts because the language of the Pledge of Allegiance is set by federal law.

Jacqueline Reis of the Telegram & Gazette staff and The Associated Press contributed to this report.